There are many different forms of data recording. For example, magnetic data recording is one of the prevailing forms of data recording. Magnetic data recording may be implemented using different types of magnetic recording media, including tapes, hard discs, floppy discs, etc. Over the years, significant developments have been made to increase the areal data recording density in magnetic data recording.
Superparamagnetism is a major limiting factor to increasing magnetic recording areal density. Superparamagnetism results from thermal excitations perturbing the magnetization of grains in a ferromagnetic material, making the magnetization distribution unstable. As the magnetic media grain size is reduced for high areal density recording, superparamagnetic instabilities become more of an issue. The superparamagnetic effect is most evident when the grain volume V is sufficiently small that the inequality KuV/kBT>40 can no longer be maintained. Ku is the material's magnetocrystalline anisotropy energy density, kB is the Boltzmann's constant, and T is in absolute temperature. When this inequality is not satisfied, thermal energy demagnetizes the individual grains and the stored data bits will not be stable. Therefore, as the grain size is decreased in order to increase the areal density, a threshold is reached for a given material Ku and temperature T such that stable data storage is no longer feasible.
The thermal stability can be improved by employing a recording medium formed of a material having a very high Ku. Large Ku lead to increase of switching field characteristic of the medium (i.e., coercivity). However, the currently available recording heads are not able to provide a sufficient or high enough magnetic writing field to write on such a medium. The magnetic field delivered from the write head to reach magnetization reversal of the grain is currently limited to approximately 10 kOe.
Heat Assisted Magnetic Recording (HAMR), sometimes referred to as optical or thermal assisted recording, has been proposed to overcome at least some of the problems associated with the superparamagnetic effect. HAMR generally refers to the concept of locally heating a recording medium with a laser to reduce the coercivity of the recording medium, so that an applied magnetic writing field can more easily direct the magnetization of the recording medium during the temporary magnetic softening of the recording medium caused by the laser. By heating the medium, the Ku or the coercivity is reduced such that the magnetic write field is sufficient to write to the medium. Once the medium cools to ambient temperature, the medium has a sufficiently high value of coercivity to assure thermal stability of the recorded information. Considerable design developments have been accomplished to generate the thermal energy and to efficiently direct the thermal energy toward the writing location on the recording medium.
It would be desirable to develop a recording medium with improved thermostability and coercivity characteristics to facilitate magnetic data recording using current transducer designs.